A rapid-transit railway such as the Shinkansen adopts an AC electrification system to secure large power. Since power is supplied from individual substations, a section is provided to isolate a neighbor power source. Such a configuration is specifically illustrated in FIG. 11. An dead section 100 is disposed at an appropriate place in order to isolate the power supplies G1 and G2 from each other. The dead section 100 has a length set to about 1 km. When a train 101 passes through the dead section 100, a section switch VS1 is first closed to charge the dead section 100. While the train 101 passes through the dead section 100, the section switch VS1 is opened and the section switch VS2 is closed, so that a charge source for the dead section 100 is changed from G1 to G2. Discharged time during this operation is controlled to about 0.05 to 0.3 sec, so that the train 101 can pass through the dead section 100 still at high speed without coasting. When the train 101 has passed through the dead section 100, the section switch VS2 is opened.
Examples of existing switches include a switch described in Patent Literature 1 that is however different from the above-described switch for the rapid-transit railway. Patent Literature 1 describes a DC breaker for DC current breaking in which a plurality of energizing vacuum breakers and breaking vacuum breakers disposed in parallel to the energizing vacuum breakers are provided between a DC power supply and a reactor as a load, and the breaking vacuum breakers are disposed in parallel to one another. In Patent Literature 1, the energizing vacuum breakers are provided separately from the breaking vacuum breakers. During energization, the breaking vacuum breakers are opened, while the energizing vacuum breakers are closed. On the other hand, during braking, the breaking vacuum breakers are first closed, and then the energizing vacuum breakers are opened to commutate a current to each breaking vacuum breaker, and then the breaking vacuum breakers disposed in series are sequentially opened, so that the DC current is finally decreased to zero through attenuation according to a predetermined time constant given by a series circuit of resistances provided in parallel to the breaking vacuum breakers and the reactor.